1. Field of the Invention
The present invention relates to a capacitor type seat sensor which is installed in a vehicle seat to sense the presence of an occupant on the vehicle seat and can prevent conductive panels as component parts of the seat sensor from becoming wrinkled.
2. Description of Related Art
These days, an air bag system is installed in a vehicle such that in case of a crash, an air bag can be deployed in response to a signal from an acceleration sensor so as to prevent an occupant from being injured.
In case of a crash, it is necessary to determine whether the air bag must be deployed or not and, when it is determined to deploy the air bag, it is required that an inflator be actuated under precise control.
In the course of this, the presence of an occupant on a vehicle seat, the weight of the occupant, etc. should be taken into consideration. In order to obtain such information, a capacitor type seat sensor is used to detect the presence of an occupant on a vehicle seat, and a weight sensor is used to sense the weight of the occupant to thereby distinguish between an adult and a child.
Referring to FIG. 1, in a conventional capacitor type seat sensor, three sheets of protective panels 10 made of felt are stacked one upon another, and conductive panels 22 and 24 are interposed between the protective panels 12, 14 and 16, so that a control unit 30 can determine the presence of an occupant on a vehicle seat owing to an increase or a decrease in capacitance.
Because most of the human body is made up of water, when an occupant sits on a vehicle seat, the dielectric constant of the conductive panels 22 and 24 changes, and therefore, the presence of an occupant on a vehicle seat can be detected by a change in capacitance.
FIG. 2 illustrates the installation structure of the conventional capacitor type seat sensor. Character lines 52 are formed left and right on a vehicle seat 50. Both side ends of the protective panels 10 are fastened along the character lines 52 by means of hog rings 60, etc. The conductive panels 20 are interposed between the protective panels 12, 14 and 16 using an adhesive or some other means.
The conventional capacitor type seat sensor has a problem in that hog rings cannot be used at the front ends of the protective panels 10 due to the deterioration of the occupant's riding comfort and as a result, front end portions 18 of the protective panels 10 extending beyond the foremost hog rings 62 are likely to be wrinkled or pushed rearward due to the occupant's repeated boarding and deboarding. As the front end portions 18 of the protective panels 10 are pushed rearward, front end portions 26 of the conductive panels 20 are also pushed rearward. In this case, because the front end portions 26 of the conductive panels 20 are likely to be wrinkled, a situation can occur in which the capacitor type seat sensor erroneously detects the presence of an occupant on a vehicle seat and causes inappropriate deployment of an air bag.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.